Which pneumatic actuator converts compressed air flow into rotary mechanical power?

The selection of the motor as the correct answer is grounded in its function as a pneumatic actuator designed to convert compressed air flow into rotary mechanical power. This process typically involves the use of a vaned rotor or similar mechanism that spins in response to the air pressure, thereby producing rotational movement suitable for various applications, including driving machinery or tools.

In contrast, both single acting and double acting cylinders are designed to produce linear motion rather than rotary motion. A single acting cylinder moves in one direction while relying on an external force (like a spring) to return to its original position, and a double acting cylinder provides power in both directions by using compressed air for both extending and retracting the cylinder. Consequently, while both of these cylinder types are effective in converting compressed air into mechanical force, they do so in a linear format, which does not meet the criteria of rotary motion.

Therefore, the motor is the only option that specifically achieves the conversion of air flow into rotary mechanical power.